docs(client): Add client_json example

Closes #1581

Cargo.toml

@@ -46,6 +46,9 @@ spmc = "0.2"
 url = "1.0"
 tokio-fs = "0.1"
 tokio-mockstream = "1.1.0"
+serde = "1.0"
+serde_derive = "1.0"
+serde_json = "1.0"
 
 [features]
 default = [
@@ -77,6 +80,11 @@ name = "client"
 path = "examples/client.rs"
 required-features = ["runtime"]
 
+[[example]]
+name = "client_json"
+path = "examples/client_json.rs"
+required-features = ["runtime"]
+
 [[example]]
 name = "echo"
 path = "examples/echo.rs"